Corrosion inhibitors



United States 2,857,333 CORROSION INHIBITORS Ralph B. Thompson,Hinsdale, 11]., :a'ssignor to Universal 011 Products'Company, DesPlaines, Ill., a corporation of Delaware No Drawing. Application June20, 1956 Serial N0. 592,487

4 Claims. (Cl. 252-389) This invention relates to corrosion inhibitors,and more particularly to an inhibitor sion of metal surfaces by water,associated in relatively small quantities, with organic materials.

In the manufacture, handling, transportation and/ or use of variousorganic substances, corrosion problems occur due to the presence ofvarying amounts of Water in solution or in suspension in the organicsubstances. Illustrative organic substances include hydrocarbondistillates as gasoline, jet fuel, kerosene, lubricating oil, fuel oil,diesel oil, crude oil, etc. Other specific Oils include cutting oils,soluble oils, slushing .oils,,rolling oils, etc. which may be ofmineral, animal or vegetable origin. Various coating compositionsinclude grease, waxes, household oils, paints, lacquers, etc. Otherorganic substances include alcohols, ketones, esters, ether-s, dioxane,

amino "compounds, amides, etc. In spite of all reason- 'able andpractical precautions whichare taken to avoid the presence of water, anappreciable quantity of water separation is found as a film or in minutedroplets in the pipe "line or on'coiitainer walls or even in small poolsat the bottom of the container. This results in corrosion of the metalsurfaces and contamination of the organic substance by the corrosionproducts.

A recently proposed corrosion inhibitor of especial effectiveness is analkyl acid phosphate salt of an N-alkyldiam'ino'alkane, and particularlysuch a salt in which at least one of the alkyl groups'constituting theester portion of the acid phosphate contains at least 6 and preferablyat least 8 carbon atoms. Particularly effective corrosion inhibitorsinclude the mono-octyl acid orthophosphate salt of N-tallow-1,3diaminopropane, dioc'tyl acid orthophosphate salt of N-tallo'w-1,3dia'minopropane, mixture of monoand di'octyl acid orthoph'o'sphate saltsof N-tallowl,3-diaminopropane, similar salts or mixed salts in which thealkyl substituent of the acid orthophosphate 'com prises nbnyl,'decyLundecyl, d'odecyl, tridecyl, tetradecyl, pentadecyl, hex'adecyl,heptadecyl, octadecyl, non'odecyl, eicosyl, etc.

Other suitable corrosion inhibitors comprise alkyl acid orthophosphatesalts of N-alkyl-l,3-diaminopropahes in which the alkyl group is derivedfrom lauric acid, coconut fatty acid, 'so'ya fatty acid, etc. and thusmay be des ignated as an alkyl acid orthophosphate salt of N-lauryl- 1,3diaminopropane, N coco 1,3 diaininopropane, N- soya-l,3-diaminopropane,etc.

The N-tallow-l,3-diaminopropane contains mostly 16 to 18 carbon atomsper alkyl group, although it contains a small amount of 14 carbon atomalkylgroup. The N-coco-l,3-diaminopropane contains alkyl groups havingfrom 8 to l8'carbon atoms, predominating in 12 and 14 carbon atom alkylgroups. The N-soya-l,3-diaminopropane predominates in alkyl groupscontaining 18 carbon atoms per group, although it contains a smallamount of a 16 carbon atom alkyl group.

While the N-alkyl-l,3-diaminopropanes are preferred, it is understoodthat other suitable N-alkyl-diaminoalkanes may be employed including forexample, N-alkylfor use in preventing corro- 2,857,333 Patented Oct. 21,1958 1,2-diaminoethanes, N-alkyl-l,2=diaminopropanes,N-alky1-l,2-diaminobutanes, N-alkyl-1,3=diaminobutanes, N- alkyl1,4-diaminobutanes, N-alkyl-l,Z-diaminopentanes, N alkyl1,3-diaminopentanes, N-alkyl-1,4-diaminopentanes,N-alkyl-l,S-diaminopentanes, N-alkyl-1,2-diaminohexanes, N alkyl 1,3diaminohexanes, N-alkyl-l,4-diaminohexanes, N-alkyl-1,5-diaminohexanes,N-alkyl-l,6- diaminohexanes, etc.

While the alkyl acid orthophosphate salts are preferred, in some casesthe alkyl acid pyrophosphate salts may be employed. These alkyl acidpyrophosphate salts likewise contain at least 6 and preferably at least8 carbon atoms in at least one of the alkyl groups and these are saltsof the N-alkyl-diaminoalkanes hereinbefore set forth.

It is understood that the various alkyl acid orthophosphate and alkylacid pyrophosphate salts of N-alkyl-diaminoalkanes are not necessarilyequivalent in the same or diiferent substrate. However, all of them willshow some effectiveness as a corrosion inhibitor and may be used inaccordance with the present invention.

As hereinbefore set forth, the alkyl acid orthphosphate andpyhophosphate salts of the N-alkyl-diaminoalkanes are effectivecorrosion inhibitors. However, in some cases, they do not meet themilitary specifications for water tolerance. The present invention isdirected to a corrosion inhibitor composition, and ;use thereof,comprising the alkyl acid phosphate 'saltsof-N-alkyl-diaininoalkanescontaining a minor proportion of "a specific mixed condensation productwhich permits the inhibitor to pass the water tolerance test. As will beshown by the following examples, the condensation product is prepared bythe use of particular reactants.

In one embodiment the present invention relates to a corrosion inhibitorcomprising an alkyl acid phosphate salt of an N-alkyl-diaminoalkane andthe mixed condensation product of N,N-diethyl-ethaholamine andN-methyl-diethanolamine with the reaction product .of a te'rpene and acompound selected from the group consisting of an alpha,beta-unsaturatedpolycarboxylic acid, anhydride and ester thereof.

In another embodiment the present invention relates to a non-corrosivecomposition of matter comprising an organic material coming in contactwith water during the useful life thereof, said organic materialcontaining. dissolved therein a corrosion inhibitor composition asherein set forth.

From the preceding description, it will benot'ed that the corrosioninhibitor comprises an alkyl acid phosphate salt of anN-alkybdiaminoalkane together with a particular mixed condensationproduct. The mixed condensation product is formed by the mixedcondensation of N,N-diethyl-ethanolamine and N-methyl-diethanolaminewith the reaction product of a'terpene and an alpha,betaunsaturatedpolycarboxylic acid, anhydride or ester thereof. V I

in a preferred embodiment the N,N-die'th'yl-etharrolamine is employed ina concentration of 0.3 to 0.6 equivalents per 1 equivalent of theterpene reaction product. In the preferred embodiment, one equivalent ofthe total of the two alkanolamines are condensed with one equivalent ofthe terpene reaction product. This establishes the preferredconcentration of the N-methyl-diethan'olamine as 0.4 to 0.7 equivalentsper one equivalent of the terpene reaction product.

The reaction product of the terpene and alpha,betaunsaturatedpolycarboxylic acid, anhydride or ester will comprise primarily theanhydride but the acid and/or ester also will be present. Any suitableterpeni'c compond may be reacted with any suitablealpha,beta-unsaturated polycarboxylic acid, anhydride or ester to termthe reaction product for subsequent condensation with theN-alkyl-diethanolamincs. In one embodiment, a terpene hydrocarbon havingthe formula C H is employed, including alpha-pinene, beta-pinene,dipentene, d-limonene, l-limonene and terpinoline. These terpenehydrocarbons have boiling points ranging from about 150 to about 185 C.In another embodiment the terpene may contain three double bonds inmonomeric form, including terpene as allo-o-cymene, o-cymene, myrcene,etc. Other terpenic compounds include alpha-terpinene, p-cymene, etc.

As hereinbefore set forth, the terpene is reacted with analpha,betausaturated polycarboxylic acid, anhydride or ester thereof.Any unsaturated polycarboxylic acid having a point of unsaturationbetween the alpha and beta carbon atoms may be employed. Illustrativeunsaturated dicarboxylic acids include maleic acid, fumaric acid,citraconic acid, mesaconic acid, aconitic acid, itaconic acid. While thedicarboxylic acids are preferred, it is understood thatalpha,beta-unsaturated polycarboxylic acids containing three, four ormore carboxylic acid groups may be employed. Furthermore, it isunderstood that a mixture of alpha,beta-unsaturated polycarboxylic acidsand particularly of alpha,beta-unsatu'rated dicarboxylic acids may beused.

While the alpha,beta-unsaturated polycarboxylic acid may be employed,advantages appear to be obtained in some cases when using the anhydridesthereof. Illustrative anhydrides include maleic anhydride, citraconicanhydride, aconitic anhydride, itaconic anhydride, etc. It is understoodthat a mixture of anhydrides may be employed and also that the anhydridemay contain substituents and particularly hydrocarbon groups attachedthereto. Furthermore, it is understood that the various anhydrides arenot necessarily equivalent. Also, it is understood that esters of thealpha,beta-unsaturated polycarboxylic acids may be employed, the estergroup being selected from alkyl. alkaryl, aralkyl, aryl and cycloalkylsubstituents replacing one or more of the hydrogen atoms of thecarboxylic acid groups.

The reaction of terpene and alpha.beta-unsaturated acid, anhydride orester generally is effected at a temperature of from about 150 to about300 C., and preferably of from about 160 to about 200 C. The time ofheating will depend upon the particular reactants and may range from 2hours to 24 hours or more. When desired, a suitable solvent may beutilized. Following the reaction, impurities or unreacted materials maybe removed by vacuum distillation orotherwise, to leave a resinousproduct which may be a viscous liquid or a solid.

A terpene-maleic anhydride reaction product is available commerciallyunder the trade name of Petrex acid. This acid is a stringy,yellow-amber colored mass and is mostly dibasic. It has an acid numberof approximately 530, a molecular weight of approximately 215 and asoftening point of 40-50 C.

As hereinbefore set forth, one equivalent of the total pf the twoethanolamines is reacted with one equivalent .of the terpene reactionproduct. The equivalents of the alkanolarnines is determined by the sumof the hydroxyl groups in the two alkanolarnines. The equivalent of theterpene reaction product is determined by the number of carboxylic acidor potential carboxylic acid groups.

The condensation of the alkanolarnines and terpene reaction product iseffected in any suitable manner. The condensation generally is effectedat a temperature above about 80 C. and preferably at a highertemperature which usually will not exceed about 200 C., although higheror lower temperatures may be employed under certain conditions. Theexact temperature will depend upon whether a solvent is used and, whenemployed, on the particular solvent. For example, with benzene as thesolvent, the temperature will be in the order of 80 C., with toluene thetemperature will be in the order of 120 C., and with xylene in the orderof 150-155 C. Other preferred solvents include cumene, naphtha, decalin,etc. Any suitable amount of the solvent may be employed but preferablyshould not comprise a large excess because this will tend to lower thereaction temperature and slow the reaction. Water formed during thereaction may be removed in any suitable manner including, for example,by operating under reduced pressure, by removing an azeotrope ofwater-solvent, by distilling the condensation product at an elevatedtemperature, etc. A higher temperature may be utilized in elfecting thereaction in order to remove the water as it is being formed.

The mixed condensation product is incorporated in the alkyl acidphosphate salt of N-alkyl-diaminoalkane in a concentration of from about0.1 to about 5% by weight of the salt, although higher concentrations upto 25% may be used in some cases. For ease of handling, the inhibitorcomposition is prepared as a solution in a suitable solvent. In onemethod, the alkyl phosphate salt of N-alkyl-diaminoalkane is prepared asa solution in a solvent, and the mixed condensation product ofN,N-diethyl-ethanolamine and N-methyl-diethanolamine with the terpenereaction product is incorporated in the solution. Any suitable solventmay be employed and preferably comprises a hydrocarbon distillate orhydrocarbon fraction including benzene, toluene, xylene, cumene, etc.The solution may contain from about 10 to by weight of activeconstituents and preferably from about 35 to about 70% by weight ofactive constituents.

The amount of inhibitor composition to be incorporated will depend uponthe particular organic substrate in which it is to be used. In general,the inhibitor composition Will be used in a concentration of less thanabout 5% by weight and thus may range from about 0.0001% to about 5% byweight and still more preferably within the range of from about 0.001%to about 1% by weight of the organic substance. It is understood thatthis inhibitor composition may be used along with other additives usedfor specific purposes in the organic substrate and, when desired,theinhibitor composition of the present invention may be admixed withthe other additive or additives and marketed as a single commodity ofmultiple purposes.

As hereinbefore set forth, the inhibitor composition of the presentinvention may be utilized in any organic substance containing orcontacting water and causing corrosion of metals. In one embodiment theinhibitor composition is added directly to the organic substance andintimately mixed to obtain distribution of the inhibitor composition inthe organic substrate. When used in plant equipment, the inhibitorcomposition of the present invention may be introduced into thefractionator or pipe line of the plant equipment, to thereby preventcorrosion of the plant equipment. Generally, a sufficient concentrationof the inhibitor composition will be employed so that a portion of theinhibitor composition is retained in the organic substance itself andserves to retard corrosionof metal piping or containers through or intowhich the organic substance is subsequently passed. a

The following examples are introduced to illustrate further the noveltyand utility of the present invention but not with the intention ofunduly limiting the same.

EXAMPLE I This example illustrates the effectiveness of a mixture ofmonoand dioctyl acid orthophosphate salt of N-tallow-1,3-diaminopropaneas a corrosion inhibitor. The salt was prepared as a 50% by weightsolution in toluene.

This salt was tested by the ASTM Steam Turbine Oil Corrosion Test (ASTMD665-52T) whichtest has been found to correlate with the resultsobtained in the storage of oil in storage tanks. In this test, 300 cc.of Nujol, to which 30 cc. of synthetic sea water is added, is placed ina beaker open to the atmosphere. A highly polished mild carbon steel rodis suspended in the oil-water suspension, heated to and maintained at140 F., with stirring, for 48 hours. The steel rod then is inspected andthe corrosion reported as light, medium or heavy. In addition, theportion of the rod covered with rust is also reported as a number of 1/of the rod covered with rust, as well as reporting the extent ofpitting.

The results of this test are shown in the following table, along withthe results obtained when not using any inhibitor. The percent inhibitorused is on the basis of active constituents, exclusive of solvent.

Table'l Inhibitor Cori psion, Coverage Fitting fiet v y 10 Deep. Clean 0None.

EXAMPLE II cedure then is to shake the mixture for 2 minutes, allow itto stand for 5 minutes, after which it is inspected. In order to passthis test, there must be a clear break. In other words, there must be nocloudiness at the interface of oil and water. The results are reportedas either pass or fail.

When tested in the above manner, the corrosion inhibitor of Example IWill not pass this test. On the other hand, a sample of the sameinhibitor solution containing 0.5% by weight of the mixed condensationproduct hereinafter described passed the water tolerance test.

The mixed condensation pro-duct referred to above was prepared by thecondensation of 0.4 equivalents of N,N-diethyl-ethanolamine and 0.6equivalents of N- rnethyl-diethanolamine with 1 equivalent of Petrexacid. This condensation was effected using xylene as the solvent, afterwhich the xylene was removed by distilling under vacuum.

EXAMPLE III A similar water tolerance test for jet fuel is conducted insubstantially the same manner except that IP4 jet fuel is used. Thistest is designated as MIL I--5624.

When a sample of the inhibitor described in Example I was tested in thismanner, it failed to pass the water tolerance test for JP-4 fuel. On theother hand, a sample containing 1.5% by weight of the inhibitor solutionof the mixed condensation product described in Example II did pass theJP4 water tolerance test.

EXAMPLE IV A sample of the inhibitor described in Example I and a sampleof the inhibitor described in Example II were each separately testedaccording to the method of specifications MIL-I-25017. This test issubstantially the same as the ASTM Steam Turbine Oil Corrosion Testhereinbefore described.

When evaluated according to this test, the results when using thephosphate inhibitor of Example I and the inhibitor composition ofExample II were substantially the same. This demonstrates that theincorporation of the mixed condensation product did not deleteriouslyaffect the potency of the corrosion inhibitor.

EXAMPLE V As hereinbefore set forth, it is preferred that the N,N-diethyl-ethanolamine is utilized in the condensation in a concentrationof from 0.3 to about 0.6 equivalents per 1 equivalent of the terpenereaction product. Accordingly, the N-methyldiethanolamine is used in aconcentration of from about 0.4 to about 0.7 equivalents per 1equivalent of the terpene reaction product.

Mixed condensation products using 0.05 and 0.15 equivalents ofN,N-diethyl-ethanolamine and 0.95 and 0.85 equivalents ofN-methyl-diethanolarnine, respectively, per 1 equivalent of Petrex acidwere prepared. These mixed condensation products were not readilysoluble in the alkyl acid phosphate inhibitor and, therefore, maypresent a problem in preparing a single inhibitor composition containingthese components. While these components may be added separately to theorganic substrate, this procedure generally is not as desirable ashaving a single composition. For this reason, it is preferred that theN-diethylethanolamine be utilized in a concentration of at least 0.3equivalents per 1 equivalent of Petrex acid.

'A mixed condensation product was prepared using 0.8 equivalents ofN-diethyl-ethanolamine and 0.2 equivalents of N-methyl-diethanolamineper 1 equivalent of Petrex acid. The use of this mixed condensationproduct in the alkyl acid phosphate inhibitor appeared to present anemulsion problem when used in the JP-4 test along with anothercommercial additive. Generally, it is preferred that any additive iscompatible with other additives which may be used in the organicsubstrate and, for this reason, it is preferred that theN,N-diethyl-ethanolamine is not used in the condensation in aconcentration greater than about 0.6 equivalents per 1 equivalent ofPetrex acid.

EXAMPLE VI The inhibitor composition described in Example II was testedin the copper strip corrosion method ASTM- Dl3055T. This test isconducted for 2 hours at 212 F. The results of this test are reported as1A, which indicates that the inhibitor composition was effective inpreventing corrosion. The appearance of the fuel oil was clear.

Furthermore, the inhibitor composition of Example II was soluble ingasoline to an extent about 10 times the maximum permissibleconcentration specified in MILI- 25017 specifications.

EXAMPLE VII A similar set of tests as indicated in Example VI was runusing JP-4 fuel. Here again, the copper strip corrosion test gave therating of 1B, which indicates effective corrosion prevention. Also, theappearance of the fuel was clear. Furthermore, the inhibitor compositionwas completely soluble at about 10 times the maximum concentrationpermitted according to these specifications.

I claim as my invention:

1. A corrosion inhibitor composition comprising (1) an alkyl acidphosphate salt of an N-alkyl-diaminoalkane in which the alkyl group ofthe acid phosphate contains from about 6 to about 20 carbon atoms andthe alkyl group of said diaminoalkane contains from about 8 to about 18carbon atoms, and (2) from about 0.1% to about 25% by weight of saidsalt of the mixed condensation product of (a) one equivalent ofN,N-diethyl-ethanolamine and N-methyl-diethanolamine with (b) one equivalent of the reaction product of a terpene having the formula C H and aboiling point ranging from about to about C. with a compound selectedfrom the group consisting of an alpha, beta-unsaturated polycarboxylicacid, anhydride and ester thereof, said terpene and said compound havingbeen reacted at a temperature of fro-m about 150 to about 300 C. to formsaid reaction product, and said N,N-diethyl-ethanolamine andN-methyl-diethanolamine having been condensed with said reaction productat a temperature of from about 80 to about 200 C. to form said mixedcondensation product.

2. A corrosion inhibitor composition comprising (1) an alkyl acidphosphate salt of an N-alkyl-diaminoalkane in which the alkyl group ofthe acid phosphate contains from about 6 to about 20 carbon atoms andthe alkyl group of said diaminoalkane contains from about 8 to about 18carbon atoms, and (2) from about 0.1% to about 25% by weight of saidsalt of the mixed condensation product of (a) one equivalent ofN,N-diethy1-ethanolamine and N-methyl-diethanolarnine with (b) oneequivalent of the reaction product of maleic anhydride with a terpenehaving the formula C H and a boiling point ranging from about 150 toabout 185 C., said terpene and maleic anhydric having been reacted at atemperature of from about 150 C. to about 300 C. to form said reactionproduct, and said N,N-diethyl-ethanolamine and N-methyl-diethanolaminehaving been condensed with said reaction product at a temperature offrom about 80 to about 200 C. to form said mixd condensation product.

3. A corrosion inhibitor composition comprising (1) an octyl acidphosphate salt of an N-tallow-1,3-diamino-- propane and (2) from about0.1% to about 25% by weight of said'salt of the mixed condensationproduct of (a) one equivalent of N,N-diethyl-ethanolamine andN-methyl-diethanolamine with (b) one equivalent of the reaction productof maleic anhydride with a terpene having the formula C H and a boilingpoint ranging from about 150 to about 185 C., said terpene and maleicanhydride having been reacted at a temperature of from about 150 toabout 300 C. to form said reaction product, and saidN,N-diethylethanolamine and N-methyl-diethanolamine having beencondensed with said reaction product at a temperature of from about toabout 200 C. to form said mixed condensation product.

4. A corrosion inhibitor composition comprising (1) a mixture of monoanddioctyl acid phosphate salts of an N-tallow-1,3-diaminopropane and (2)from about 0.1% to about 25 by weight of said salts of the mixedcondensation product of (a) one equivalent of N,N-diethylethanolamineand N-methyl-diethanolamine with (b) one equivalent of the reactionproduct of maleic anhydride with a terpene having the formula C I-I anda boiling point ranging from about to about C., said terpene and maleicanhydride having been reacted at a temperature of from about 150 toabout 300 C. to form said reaction product, and saidN,N-diethyl-ethanolamine and N-methyl-diethanolamine having beencondensed with said reaction product at a temperature of from about 80to about 200 C. to form said mixed condensation product.

References Cited in the file of this patent UNITED STATES PATENTS2,318,034 Wayne May 4, 1943 2,371,851 Smith et a1 Mar. 20, 19452,568,743 Kirkpatrick Sept. 25, 1951 2,728,647 Vaughn Dec. 27, 1955OTHER REFERENCES Duomeens, Armour Chemical Div. brochure, received inPatent Office February 21, 1956, pages 1 and 5.

1. A CORROSION INHIBITOR COMPOSITION COMPRISING (1) AN ALKYL ACIDPHOSPHATE SALT OF AN N-ALKYL-DIAMINOALKANE IN WHICH THE ALKYL GROUP OFTHE ACID PHOSPHATE CONTAINS FROM ABOUT 6 TO ABOUT 20 CARBON ATOMS ANDTHE ALKYL GROUP OF SAID DIAMINOALKANE CONTAINS FROM ABOUT 8 TO ABOUT 18CARBON ATOMS, AND (2) FROM ABOUT 0.1% TO ABOUT 25% BY WEIGHT OF SAIDSALT OF THE MIXED CONDENSATION PRODUCT OF (A) ONE EQUIVALENT OFN,N-DIETHYL-ETHANOLAMINE AND N-METHYL-DIETHANOLAMINE WITH (B) ONEEQUIVALENT OF THE REACTION PRODUCT OF A TERPENE HAVING THE FORMULAC10H16 AND A BOILING POINT RANGING FROM ABOUT 150* TO ABOUT 185*C. WITHA COMPOUND SELECTED FROM THE GROUP CONSISTING OF AN ALPHA,BETA-UNSATURATED POLYCARBOXYLIC ACID, ANHYDRIDE AND ESTER THEREOF, SAIDTERPENE AND SAID COMPOUND HAVING BEEN REACTED AT A TEMPERATURE OF FROMABOUT 150* TO ABOUT 300*C. TO FORM SAID REACTION PRODUCT, AND SAIDN,N-DIETHYL-ETHANOLAMINE AND N-METHYL-DIETHANOLAMINE HAVING BEENCONDENSED WITH SAID REACTION PRODUCT AT A TEMPERATURE OF FROM ABOUT 80*TO ABOUT 200*C. TO FORM SAID MIXED CONDENSATION PRODUCT.